In general, flue gas from power plants using coal combustion is one of the primary sources of CO2 emission. To mitigate global warming caused by emission of greenhouse gases such as CO2, technologies developed to remove CO2 from various emissions (e.g., power plant emissions) and its sequestration (carbon capture and sequestration (CCS)) should not incur more than a minimum of additional energy consumption.
For example, conventional CO2 absorption-stripping processes using aqueous monoethanolamine (MEA) solution can increase the cost of electricity (COE) generation substantially. As such, a reduction of steam regeneration cost, a major contributor to energy consumption, is needed among a few others contributing to the large increase in the COE.
In general, various flue gas CO2 removal techniques are available. For example, amine absorption, adsorption, condensation, membrane permeation, and chilled ammonia-based processes have been investigated.
Membrane contactors have been studied for CO2 removal. For example, Kosaraju et al. identified a reactive nonvolatile amine in an aqueous solution and studied CO2 absorption and stripping using two separate polypropylene (PP) hollow fiber-based conventional membrane contactors for over 55 days. See, e.g., Kosaraju et al., Hollow Fiber Membrane Contactor Based CO2 Absorption-Stripping Using Novel Solvents and Membranes, Ind. Eng. Chem. Res. 44 (2005) 1250-1258.
Li and Chen (Review of CO2 Absorption Using Chemical Solvents in Hollow Fiber Membrane Contactors, Sep. and Purif. Technol. 41 (2005) 109-122) provide an earlier review of membrane contactors for CO2 removal.
Ionic liquids have been studied as solvents for use in membrane contactors. Albo et al. studied CO2 capture in the ionic liquid [emim][EtSO4] using a polypropylene (PP) hollow fiber membrane contactor. See, e.g., Albo et al., Carbon Dioxide Capture from Flue Gases using a Cross-flow Membrane Contactor and the Ionic Liquid 1-Ethyl-3-methylimidazolium Ethyl sulfate, Ind. Eng. Chem. Res. 49 (2010) 11045-11051.
Gomez-Coma et al. studied the influence of temperature in CO2 absorption in membrane contactors for two ionic liquids, [emim][EtSO4] and [emim][Ac]. See, e.g., Gomez-Coma et al., Non-dispersive Absorption of CO2 in [emim][EtSO4] and [emim][Ac]: Temperature Influence, Sep. and Purif. Technol. 132 (2014) 120-125.
Luis et al. (Non-dispersive Absorption for CO2 Capture: From the laboratory to industry, J Chem. Technol. Biotechnol. 86 (2011) 769-75) identified four challenges for membrane contactor systems for CO2 removal. These challenges are: avoid membrane wetting which decreases the performance in comparison with conventional systems; develop membranes demonstrating long-term stability (or develop cheap membranes that allow frequent replacement without high expenses); apply absorption liquids having properties that allow CO2 recovery; and simultaneously minimize the environmental impact and study of the impact of other compounds on the process efficiency.
Favre and Svendsen (Membrane Contactors for Intensified Post-combustion Carbon Dioxide Capture by Gas-liquid Absorption Processes, J. Membrane Sci. 407-408 (2012) 1-7) suggested a methodology for a better comparison of membrane contactors for CO2 removal. This methodology requires explicit consideration of the process intensification factor via an average volumetric CO2 absorption capacity.
Zhang and Wang (Gas-Liquid Membrane Contactor for Acid Gas Removal: Recent Advances and Future Challenges, COCHE, 2(2) (2013) 255-262) have provided additional perspectives on the challenges for membrane contactors in CO2 removal. This includes special considerations on prevention of pore wetting via small maximum pore size and narrow pore size distribution.
Li et al. employed a membrane contactor built out of hydrophobized microporous polyetheretherketone (PEEK) hollow fibers and demonstrated excellent CO2 absorption performance using aqueous amine solutions (40 wt %). See, e.g., Li et al., Post-combustion CO2 Capture using Super-hydrophobic, Polyetheretherketone, Hollow Fiber Membrane Contactors, J. Membrane Sci. 430 (2013) 79-86.
Thus, an interest exists for improved systems, assemblies and methods to remove CO2 from emissions, and related fabrication methods. These and other inefficiencies and opportunities for improvement are addressed and/or overcome by the systems, assemblies and methods of the present disclosure.